1. Field of the Invention
Embodiments of the invention generally relate to semiconductor processing, and more particularly to apparatus and method for delivery of liquid chemicals within substrate processing systems.
2. Description of the Related Art
A chip manufacturing facility is composed of a broad spectrum of technologies. Cassettes containing semiconductor substrates are routed to various stations in the facility where they are either processed or inspected. Semiconductor processing generally involves the deposition of material onto and removal (xe2x80x9cetchingxe2x80x9d) of material from substrates. Typical processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), electro-chemical plating, chemical mechanical planarization (CMP), etching, cleaning, and others. Of the above process, approximately 25% involve liquid chemical processes.
One issue regarding semiconductor processing involves the accurate delivery of liquid chemicals to tightly control the chemical concentrations within a process solution such as photoresist. Conventional liquid delivery systems take chemicals from bulk supplies, local reservoirs, or bottles and deliver them using a metering pump and/or flow meter. Metering pumps are prone to particle generation and require periodic service and calibration. There are various flow meter technologies available to measure the amount of liquid dispensed. Most are unable to provide accurate measurement for small volumes or very low flow rates. With the exception of technology employing the Coriolis effect, all are prone to error from viscosity changes, backpressure fluctuation, liquid color, temperature fluctuation, or air bubbles in the supply line. Differential pressure technology has been successfully used at low flow rates but requires a small orifice that is incompatible with some abrasive solutions. Coriolis technology is capable of more accurate mass flow measurement and is less affected by the issues listed above. However, it is a more expensive delivery method.
Substrate processing generally requires that liquid chemicals must be delivered in precise amounts on demand, be free of bubbles, be of a uniform thickness on the usable part of the substrate and minimize chemical waste due to cost and environmental concerns. Unfortunately, conventional precision liquid delivery is prone to errors due to measurement noise and liquid measurement uncertainties. Generally, liquid delivery systems are prone to noise from a variety of sources, including vibration and thermal changes. In addition, measurement noise from liquid detectors used to detect liquid levels and flow rates may contribute to the signal to noise ratio (SNR). The SNR generally limits the system measurement resolution and, therefore, the liquid delivery precision. Liquid measurement inaccuracies may also be caused by other factors such as liquid resistance within the delivery system. For example, the chemicals may partially adhere to tubing used to deliver the liquid causing resistance to liquid movement. Further, as chemicals move through the delivery system they may pick up residual chemicals from a previous processing and/or add or subtract liquid, thereby altering the delivery amount.
Air in the delivery system may also cause delivery inaccuracies. It is desirable to completely use the contents of a chemical bottle without introducing air bubbles into the delivery line. One method is to place a reservoir between the chemical bottle and the metering device, In the case of a pressurized chemical bottle, this reservoir can be periodically vented in order to remove air pockets from the system. For a non-pressurized bottle, a vacuum is typically drawn on the reservoir. Typically, a bubble sensor is used to detect air in the liquid delivery system to minimize the risk of introducing bubbles into the chemicals during chemical delivery or refill. The bubble sensor is also generally used to detect when the reservoir is empty, thus allowing the liquid delivery system to switch to a different reservoir. However, bubble sensors are often prone to errors as air bubbles introduced into the system may trigger a false empty signal. Thus, not all of the chemical may be used before the system switches to the next reservoir.
Therefore, there is a need for a liquid delivery system configured to provide controllable liquid delivery, improved liquid delivery precision, and increased liquid utilization.
Embodiments of the invention generally provide a liquid delivery system configured to provide precise delivery of liquid chemicals used in semi-conductor processing. In one embodiment, the invention provides an apparatus for delivering liquids to substrate processing systems including a frame, a plurality of load cells extending from the frame, each adapted to output signals corresponding to the liquid input and output of the apparatus, and a plurality of free hanging vessels. Each vessel is suspended from one of the plurality of load cells. Each of the plurality of free hanging vessels including at least one gas input, at least one liquid input, and at least one liquid outlet, and at least one vibration dampener disposed between each of the plurality of load cells and each of the plurality of free hanging vessels hanging therefrom, to minimize the transmission of vibration therebetween.
In another embodiment, the invention provides a liquid delivery system adapted to deliver one or more liquids to substrate processing systems. The system includes a plurality of free hanging vessels vibrationally isolated from a frame, a plurality of load cells disposed on the frame, each having one of the plurality of free hanging vessels hanging therefrom, wherein each of the plurality of load cells is adapted to output one or more signals corresponding to a weight of the one free hanging vessel attached thereto. The system also includes at least one vibration dampener positioned between the frame and each of the plurality of load cells to isolate vibration transmission therebetween. The system further includes a controller electrically coupled to the plurality of load cells and adapted to process the one or more signals therefrom to control the liquid flow of the liquid delivery system.
In another embodiment, the invention provides determining a method of delivering liquids to a substrate processing system including determining a total fluid amount to deliver, determining a first system response to compensate for system noise during liquid delivery, and determining a first liquid amount to deliver from at least one of a plurality of vessels fluidly coupled to the substrate processing system. The first liquid amount to deliver corresponds to a first deliver time associated with a delivery rate and the first system response. The method includes delivering the first liquid amount to the substrate processing system then determining a second liquid amount to deliver to the substrate processing system based on the first liquid amount delivered thereto and the delivery rate, where the second liquid amount delivered corresponds to a second delivery time. Then delivering the second liquid amount to the substrate processing system, wherein the summation of the first liquid amount delivered and the second liquid amount delivered is within a range of the total fluid amount to be delivered.
A method of delivering liquids from liquid sources to one or more substrate processing systems using a liquid delivery apparatus, including providing at least one signal to a controller from a load cell corresponding to a weight of the vessel, then processing the at least one signal to determine a first system response. The first system response based on at least one of system noise and a system delivery error during liquid delivery. The method includes delivering a first liquid amount for a first delivery time at a delivery rate, and delivering a second liquid amount for a second delivery time based on the first liquid amount delivered, wherein the first liquid amount delivered and second liquid amount delivered total to within a range of a specified liquid delivery amount.